Objective: This study aimed to investigate the expression of Ki-67, epithelial cadherin (E-cadherin), mesothelin, and their correlations with clinicopathological features of serous borderline ovarian tumors (SBOTs). Materials and Methods: Immunohistochemistry was conducted to investigate the expression of a cellular proliferation-related factor (Ki-67) and metastasis-related factors (E-cadherin and mesothelin) in 41 cases of SBOTs, 30 benign ovarian tumor tissues, and 30 malignant ovarian tumor tissues. Results: The results showed that the expression rate of Ki-67 (46.3%) in SBOTs was higher than that in benign tumors (6.7%), but lower than that in ovarian carcinomas (80%). SBOTs significantly differed from benign ovarian tumors (p < 0.01) and carcinoma (p < 0.01). The positive expression rate of Ki-67 was significantly correlated with FIGO stage and peritoneal implantation of SBOTs (p < 0.01). The expression rate of E-cadherin was significantly lower in ovarian carcinomas (56.7%) than in SBOTs (80.5%) and benign ovarian tumors (90%; p < 0.05). The mesothelin expression in ovarian carcinomas and SBOTs significantly differed from that in benign ovarian tumors (p < 0.01). The positive expression rate of mesothelin was related to the serum CA125 level (p < 0.05). The expression of Ki-67 was positively correlated with the expression of E-cadherin and mesothelin in SBOTs. Conclusion: SBOTs generally behave in a benign manner. Ki-67, E-cadherin, and mesothelin may play an important role in the oncogenesis and progression of SBOT. Patients with Ki-67 and mesothelin overexpression and low E-cadherin expression should be followed up.